Human hair is the keratin-containing threadlike outgrowth extending from hair follicles in the skin. In humans, hair generally serves protective, sensory, and sexual attractiveness functions. A mature hair shaft is composed of three, and sometimes four, basic structures. The cuticle is the thick outer protective covering consisting of flat overlapping scale-like layers. The cortex is located inside, and is surrounded by, the cuticle. The cortex contains fibrous proteins, which are aligned along the length of the hair axis. Thicker hairs often contain one or more porous regions, the medulla, located near or at the center of the hair shaft. The fourth basic component is the intercellular cement, which glues or binds the cells together and provides the main pathway for diffusion into the hair fibers. Melanocytes, which produce melanin, the pigment responsible for hair color, are generally contained in the cortex and the base of the bulb of the hair shaft. Essential nutrients and oxygen are carried to the growing hair through capillaries around the base of the bulb. The hair follicle cycle is a complex process and entails involvement of cell differentiation, epithelial-mesenchymal interactions, stem cell augmentation, pattern formation, apoptosis, cell and organ growth cycles, and pigmentation. The most important theme in studying the cycling of hair follicle is that the follicle is a regenerating system. By traversing the phases of the cycle (growth, regression, resting, shedding, then growth again), the follicle demonstrates the unusual ability to completely regenerate itself. The basis for this regeneration rests in the unique follicular epithelial and mesenchymal components and their interactions. Recently, some of the molecular signals making up these interactions have been defined. They involve gene families also found in other regenerating systems such as fibroblast growth factor, transforming growth factor-xcex2, Wnt pathway, Sonic hedgehog, neurotrophins, and homeobox. (K S Stenn and R Pauls, Physiol Rev 2001 Jan; 81(1):449-494).
Normal hair follicles cycle between a growth stage (anagen), a degenerative stage (catagen), and a resting stage (telogen). The scalp hairs have a relatively long life cycle: the anagen stage ranges from two to five years, the catagen stage ranges from a few days to a few weeks, and the telogen stage is approximately three months (Fitzpatrick, T. B., et al., eds., DERMATOLOGY IN GENERAL MEDICINE (Vol. I), McGraw-Hill, Inc., 1993, pp. 290-291; Sperling, L. C., J. Amer. Acad. Dermatology (v. 25, No. 1, Part 1), pp. 1-17 (1991)). Shorter hairs found elsewhere on the body have corresponding shorter anagen duration. The morphology of the hair and the hair follicle changes dramatically over the course of the life cycle of the hair. During anagen, the hair follicle is highly active metabolically (Sperling, L. C., J. Amer. Acad. Dermatology (v. 25, No. 1, Part 1), p. 4 (1991)). The follicle comprises a follicular (dermal) papilla at the base of the follicle; epidermal matrix cells surrounding the follicular papilla and forming the base of a hair shaft; and the hair shaft that extends upwards from the papilla through the hair canal (Fitzpatrick, T. B., et al., eds., DERMATOLOGY IN GENERAL MEDICINE (Vol. I), McGraw-Hill, Inc., 1993). The matrix cells are the actively growing portions of the hair (Sperling, L. C., J. Amer. Acad. Dermatology (v. 25, No. 1, Part 1), p.6 (1991)). At catagen, the matrix cells retract from the papilla, and other degenerative changes occur (Sperling, L. C., J. Amer. Acad. Dermatology (v. 25, No. 1, Part 1), pp. 13-14 (1991)). A column of epithelial cells pushes the keratinized proximal shaft of the hair upwards (Sperling, L. C., J. Amer. Acad. Dermatology (v. 25, No. 1, Part 1), p. 3 (1991)), and cell death occurs within the follicle (Fitzpatrick, T. B., et al., eds., DERMATOLOGY IN GENERAL MEDICINE (Vol. I), McGraw-Hill, Inc., 1993, p. 291). When the hair follicle reaches the telogen stage, the existing hair has a club-shaped proximal end, and a small bud (a remnant of the epithelial column that is found in catagen) at the base of the follicle (Sperling, L. C., J. Amer. Acad. Dermatology (v. 25, No. 1, Part 1), p. 3 (1991)). A telogen hair will not grow further (Fitzpatrick, T. B., et al., eds., DERMATOLOGY IN GENERAL MEDICINE (Vol. I), McGraw-Hill, Inc., 1993, p. 291). The pigmentary system that colors hair involves melanocytes located in the matrix area of the follicle, above the follicular papilla (Fitzpatrick, T. B., et al., eds., DERMATOLOGY IN GENERAL MEDICINE (Vol. I), McGraw-Hill, Inc., 1993, p. 292). Melanin pigments produced by the melanocytes flow along dendritic processes (Fitzpatrick, T. B., et al., eds., DERMATOLOGY IN GENERAL MEDICINE (Vol. I), McGraw-Hill, Inc., 1993, p. 292). The dendritic processes are phagocytized by the differentiating matrix cells that become part of the hair shaft; degradation of the phagocytosed material results in release of melanin granules into the cytoplasm (Fitzpatrick, T. B., et al., eds., DERMATOLOGY IN GENERAL MEDICINE (Vol. I), McGraw-Hill, Inc., 1993, p. 671), thus pigmenting the hair. Alterations in normal hair pigmentation or growth may be caused by age, physiologic disease conditions, or injury especially, for example, exposure to ultraviolet-irradiation. The xe2x80x9cgrayingxe2x80x9d of hair, both normal (age-associated) and abnormal, is known as canities. Graying results from a progressive decrease in pigment present in the hair shaft, caused by loss of melanocytes (Fitzpatrick, T. B., et al., eds., DERMATOLOGY IN GENERAL MEDICINE (Vol. I), McGraw-Hill, Inc., 1993, p. 671; Gilchrest, B. A., SKIN AND AGING PROCESSES, CRC Press, 1984, p.19). A decrease in the density of hair follicles is also associated with advancing age (Gilchrest, B. A., SKIN AND AGING PROCESSES, CRC Press, 1984, p. 20). Alopecia areata is a common disease of the hair follicle, affecting about 2% of new patients attending dermatology clinics in the United States and in Britain (Price, V. H., J. Invest. Dermatol., 96:685 (1991)). In alopecia areata, the hair follicle, in response to some unknown signal or injury, is suddenly precipitated into premature telogen, and then cycles in a shortened aborted cycle in which it is repeatedly arrested part way through early anagen. The follicle may remain in this arrested state but is capable of resuming normal growth after months or years. The nature of the signal or injury and the anatomical target for this abnormality are unknown. Histologically, alopecia areata is characterized by peribulbar lymphocytic infiltrate of predominantly T helper cells (Lever, W. F. and Schaumburg-Lever, G., eds., HISTOPATHOLOGY OF THE SKIN, J. B. Lippincott Co., Philadelphia, Pa., 1990, pp. 223-224), strongly suggesting the involvement of the cellular immune system perhaps through a loss of discrimination of self and non-self antigens (Goldsmith, L. A., J. Invest. Dermatol., 96:985-1005 (1991)). Alternatively, an intrinsic abnormality in the follicular keratinocyte could be activated under the influence of internal or external triggers, which eventually may lead to cellular degeneration and peribulbar inflammatory infiltrate. However, to date no specific antigen has been identified to support the autoimmune theory and no specific intrinsic difference has been reported between normal bulbar and alopecia areata keratinocytes. The hair follicle is an epidermal derivative that undergoes cycles of growth, involution, and rest. The hair cycle has well-orchestrated kinetics regulated by interactions between mesenchymal and epithelial cells, although the intracellular signals remain unclear. There is suggestion that telogen-to-anagen progression required organized keratinocyte migration in response to mesenchymal stimuli.
Alopecia (baldness) a deficiency of hair, either normal or abnormal, is primarily a cosmetic problem in humans. Hair loss occurs in a variety of situations. These situations include male pattern alopecia, alopecia senilis, alopecia areata, diseases accompanied by basic skin lesions or tumors, and systematic disorders such as nutritional disorder and internal secretion disorders. The mechanisms causing hair loss are very complicated, but in some instances can be attributed to aging, genetic disposition, the activation of male hormones, the loss of blood supply to hair follicles, and scalp abnormalities. It is a deficiency of terminal hair, the broad diameter, colored hair that is readily seen. However, in the so-called bald person although there is a noticeable absence of terminal hair the skin does contain vellus hair, which is a fine colorless hair, which may require microscopic examination to determine its presence. This vellus hair is a precursor to terminal hair. In both women and men, the occurrence of an increased loss of hair is accompanied by the fear of becoming totally bald-headed. Besides the medical aspect, disturbances in the hair growth thus present a great personal problem for the affected person. The rate of growth of the hair amounts to about 0.35 mm per day, the hair density is from about 80,000 to 150,000 hairs per head. A loss of 100 hairs per day constitutes already a pathological effluvium. From hair follicles that remained intact, hair is able to re-grow. However, during a multiphase, lengthy re-growth, hair follicles may shrink and lead to a gradual loss of hair.
The existence of a number of pathologic syndromes depends on androgen hormones. An unexplained switch causes androgenic alopecia from the growth promoting effect of androgens on the hair follicles to hair loss. In skin, androgen mediated disorders, such as alopecia, acne vulgaris, and hirsutism, excess of the cutaneous androgens are a major nosological factor. The androgenic hormones can act only via an androgenic receptor, which is a transcription factor, a protein that interacts with a specific region of DNA. Thus, the mode of action of testosterone and its much more potent analog, 5-alpha dihydrotestoterone depends upon binding to the androgenic receptors. Only then can transcription by RNA polymerase 11 take place. In the treatment of androgenic alopecia, various antiandrogens originally developed for the treatment of prostate cancer were claimed for systemic use, but side effects of chronic therapy with these systemically absorbable substances were of concern. The U.S. Pat. No. 6,184,249 to Sovak, et al., is for the use of substituted phenylalanines that bind specifically to androgen receptor reducing the incidence of alopecia. The U.S. Pat. No. 6,174,892 to Gormley, et al., is for a method of treating and/or reversing androgenic alopecia and promoting hair growth, and methods of treating acne vulgaris, seborrhea, and female hirsutism, by administering to a patient in need of such treatment a 5-xcex1-reductase 2 inhibitor, such as finasteride.
One form of hair loss, alopecia areata, is known to be associated with autoimmune activities; hence, topically administered immunomodulatory compounds demonstrate efficacy for treating that type of hair loss. The immunosuppressant drugs FK506, rapamycin and cyclosporin are well known as potent T-cell specific immunosuppressants, and are effective against graft rejection after organ transplantation. Topical application of FK506 (Yamamoto et al., J. Invest. Dermatol., 1994,102, 160-164; Jiang et al., J. Invest. Dermatol. 1995, 104, 523-525) and cyclosporin (Iwabuchi et al., J. Dermatol. Sci. 1995, 9, 64-69) stimulates hair growth in a dose-dependent manner. The hair growth and revitalization effects of FK506 and related agents are disclosed in many U.S. patents (Goulet et al., U.S. Pat. No. 5,258,389; Luly et al., U.S. Pat. No. 5,457,111; Goulet et al., U.S. Pat. No. 5,532,248; Goulet et al., U.S. Pat. No. 5,189,042; and Ok et al., U.S. Pat. No. 5,208,241; Rupprecht et al., U.S. Pat. No. 5,284,840; Organ et al., U.S. Pat. No. 5,284,877). Other U.S. patents disclose the use of cyclosporin and related compounds for hair revitalization (Hauer et al., U.S. Pat. No. 5,342,625; Eberle, U.S. Pat. No. 5,284,826; Hewitt et al., U.S. Pat. No. 4,996,193). These patents also relate to compounds useful for treating autoimmune diseases and cite the known use of cyclosporin and related immunosuppressive compounds for hair growth. Honbo et al., in EP 0 423 714 A2 disclose the use of relatively large tricyclic compounds, known for their immunosuppressive effects, as hair revitalizing agents.To overcome the side effects of immunosuppressants, several developments have been made using nonimmunosuppressant techniques. Hamilton and Steiner disclose in U.S. Pat. No. 5,614,547 a novel pyrrolidine carboxylate compounds, which bind to the immunophilin FKBP12 and stimulate nerve growth, but which lack immunosuppressive effects. The U.S. Pat. No. 6,177,455 to Steiner, et al., is for pharmaceutical compositions and methods for treating alopecia and promoting hair growth using non-immunosuppressant pyrrolidine derivatives.
Stem cells are by definition present in all self-renewing tissues. These cells are believed to be long-lived, have a great potential for cell division and are ultimately responsible for the homeostasis of steady-state tissues. Stem cells are normally slow cycling. They can, however, be induced to enter the proliferative pool in response to certain growth stimuli. When stem cells undergo occasional cell division, they give rise to more rapidly proliferating xe2x80x9ctransient amplifying cellsxe2x80x9d (xe2x80x9cTAxe2x80x9d). Stem cells possess many of the following properties: they are relatively undifferentiated, ultrastructurally and biochemically; they have a large proliferative potential and are responsible for the long term maintenance and regeneration of the tissue; they are normally xe2x80x9cslow-cyclingxe2x80x9d, presumably to conserve their proliferative potential and to minimize DNA errors that could occur during replication; they can be stimulated to proliferate in response to wounding and to certain growth stimuli; they are often located in close proximity to a population of rapidly proliferating cells corresponding to the transient amplifying cells (xe2x80x9cTAxe2x80x9d) in the scheme of (1) stem cell to (2) TA cell to (3) terminally differentiated cell, and they are usually found in well protected, highly vascularized and innervated areas. Positive identification of stem cells has been difficult because, there are few known immunological or biochemical markers specific for epithelial stem cells. Since they are normally xe2x80x9cslow-cyclingxe2x80x9d, they cannot be labeled by single pulse administration of radioactive materials typically used to detect actively proliferating TA cells. The U.S. Pat. No. 5,756,094 to Lavker, et al., describes a method for identification of these cells by labeling these cells continuously to generate label-retaining cells (LRCs). Cotsarelis et al., J. Invest. Dermol. 1989a, 92(3) disclose a method to facilitate detection of LRCs based on the ability of slow-cycling cells to be recruited to proliferate in response to hyperplastic stimuli.
Stem cells of various epithelia share a common set of features. It is shown that in hair follicles, the heavily pigmented stem cells are located at the base, in close proximity with follicular papillae and associated vasculature. Cotsarelis, et al., Cell 1990, 61: 1329-37, show that the hair follicle stem cells were found to exist exclusively in the mid-portion of the follicle at the arrector pili muscle attachment site termed the xe2x80x9cbulgexe2x80x9d area of the hair follicle.
A number of growth factors have been reported to be useful for modulating stem cell activity. For example, cytokines such as Tumor Necrosis Factor (TNF), Epidermal Growth Factor (EGF), Transforming Growth Factor (TGF) and Interleukin-(IL-1) are believed to be useful. Cellular targets in acute graft versus host disease have been postulated to be keratinocytes with stem cell properties. Because stem cells are normally slow cycling but proliferate rapidly upon inductive stimulation, they may be attractive targets for cytokines such as TNF. EGF has been shown to have broad biological effects. Most significantly, it has the ability to induce the proliferation of basal keratinocytes. Furthermore, it has been shown to support growth during fetal development and accelerate re-epithelialization during wound healing. TGF-xcex1 has been shown to be involved in the regulation of both growth and differentiation of epithelial cells. It is known to stimulate keratinocyte growth in vitro. IL-1 is known to induce proliferative activity in epidermal cells. Keratinocytes of the basal layer of the epidermis express the high affinity (trk E and trk) and the low affinity (p75) NGF receptors (NGF-R). NGF, produced by keratinocytes, protects cells from death when it binds to NGF receptors. In cells, this NGF effect is mediated in part by induction of the protective protein Bcl-2. Interestingly, basal epidermal keratinocytes express Bcl-2 protein. Normal anagen hair follicles strongly express the p75 NGF-R and that p75 NGF-R expression is significantly reduced and limited to a few basal keratinocytes in telogen hair follicles. The U.S. Pat. No. 6,103,689 to Gilchrest, et al., is for a method for maintaining hair growth and coloration in humans by using neurotrophin ligands to prevent p75 nerve growth factor (NGF) receptor mediated apoptosis in melanocytes and keratinocytes.
Several novel techniques and preparations have been described to promote hair growth based on the various theories and techniques described above. The U.S. Pat. No. 5,607,693 to Bonte, et al., is for a cosmetic or pharmaceutical composition which comprises oxyacanthine or an extract of a plant in which it is present, such as Berberis vulgaris or barberry. One particular association is that of oxyacanthine with a saponin. This composition can be intended in particular for stimulating hair growth, retarding hair loss or combating pruritus. The U.S. Pat. No. 6,159,475 to Olguin for a hair growth formulation. The two basic main ingredients are castor oil and a special lemon extract. The U.S. Pat. No. 6,149,933 to Nelson is for a dietary supplement, which is useful for the promotion of healthy hair, and pigment restoration in human subjects is provided. The dietary supplement contains a copper salt, p-aminobenzoic acid, pantothenic acid and vitamin B6. The U.S. Pat. No. 6,013,279 to Klett-Loch is for a combination preparation for stimulating the growth of hair and skin and nails with a combination of vitamins, enzymes, and amino acids. To increase the effectiveness of the combination preparation, its use is described as a supplement to a topically applicable hair growth stimulant, in particular a thymus-containing therapeutic agent. The U.S. Pat. No. 5,972,345 to Chizick, et al., is for a natural formulation for treatment of male pattern hair loss. The formulation contains a combination of Saw Palmetto extract, African Pygeum extract, stinging nettle extract, and optionally zinc, vitamin B6 and green tea extract. The U.S. Pat. No. 6,183,749 to Park is for a dietary supplement containing herbal extracts, which promote healthy hair growth on the scalp. A composition of a dietary supplement comprising MAMMALIA PLACENTA prepared from the placenta of a mammal, FRUCTUS LIGUSTRI LUCIDI, SALVIAE MILTIORRHIZAE, PAEONIAE RUBRA, CINNAMOMI CASSIAE, MOUTAN RADICIS, and ALISMATIS PLANTAGO-AQUATICA. For increased benefit, the dietary supplement further comprising POLYGONI MULTIFLORI, FRUCTUS LYCII CHINENSIS, FRUCTUS MORI ALBAE, VACCARIAE SEGETALIS, PLATICODI GRANDIFLORI, COICIS LACHRYMA-JOBI, and ARTEMESIAE CAPILLARIS. The dietary supplement is for oral ingestion and can be prepared in the form of a tablet, capsule, powder or syrup. The U.S, Pat. No. 5,738,879 to Rine is for scalp hair treatment method and composition wherein the composition comprises deionized water, a vasodilator (such as ethyl nicotinate and/or capsicum extract), a magnesium salt, and a hydrolyzed protein. Other patents that promote multiple use of herbal extracts include the U.S. Pat. No. 5,869,059 issued to Garza teaches an herbal composition beneficial for the treatment of hemorrhoid and the U.S. Pat. No. 5,770,207 issued to Bewicke, which teaches a dietary supplement containing herbal extracts that, serves as a general relaxant. The U.S. Pat. No. 5,738,879 to Rine is for a scalp and hair treatment method and composition wherein the composition comprises deionized water, a vasodilator (such as ethyl nicotinate and/or capsicum extract), a magnesium salt, and a hydrolyzed protein.